Doubtful they are SAE sizes unless they are jeep parts. SI units(or metric in laymans terms)are more common. 10mm or so.

I would have them re-order the right rotors. Why on earth would anyone convert over the entire hub assembly just for the rotors? However, Chevy's had 6 0n 5.5 patterns for a number of years. 80's into the early 90's I think?